Metabolite profiling of green, green/red, and red lettuce cultivars: Variation in health beneficial compounds and antioxidant potential

Salad vegetables, commonly consumed at baby-leaf stages, are the most appropriate and emerging dietary source of antioxidant compounds. Screening and identification of nutrient-rich cultivars can be potentially useful to obtain a nutrient-dense diet. Thus, in this study, we explored the genetic potential of baby leaves of 23 diverse lettuce cultivars for the health-beneficial metabolites. The results showed that the composition and contents of the studied metabolites in lettuces varied significantly between cultivars and were principally dependent on leaf color. All red-leaf cultivars were rich in carotenoids, cyanidin, polyunsaturated fatty acids (PUFAs, primarily in the form of a-linolenic and linoleic acid,) total phenolic contents (TPC), and antioxidant potential. Among carotenoids, all-E-lutein was found in highest amount, followed by all-E-violaxanthin and all-E-lactucaxanthin, accounting for an average of 30%, 28% and 15% of total carotenoids, respectively. The content of total folate was recorded in the range of 6.51 (cv. Caesar Green) to 9.73 pg/g (DW) (cv. Asia Heuk Romaine). The principal component analysis (PCA) showed that the cyanidin and other phenolic compounds are the most potent scavengers of ABTS and DPPH radicals. The overall results suggested that all red-leaf lettuce cultivars have a distinct profile of phytoconstituents, which can be used as a nutrient-dense food.